Gluconeogenesis

Question 1

The role of glucagon and epinephrine in gluconeogenesis

Answer 1

• inhibit glycolysis
• stimulate gluconeogenesis by increasing cAMP conc.
• > activates cAMP dependent protein kinase
• > phosphorylation and inactivation of pyruvate kinase

Question 2

Location

Answer 2

mainly in the liver but also kidneys

Question 3

Synthesis of glucose from non-carbonate compounds

Answer 3

• Lactate: oxidized by NAD+, catalyzed to pyruvate by lactate DH
• Amino acids: degradation of muscle proteins, converted to pyruvate and nitrogen to urea.
• Glycerol: triaglycerols react with ATP and form dihydroxyacetone phosphate

Question 4

Gluconeogenesis activated by

Answer 4

glucagon
acidosis
glucocorticoids

Question 5

Pyruvate -> Oxaloacetate

Answer 5

• IRREVERSIBLE
• enzyme: PYRUVATE CARBOXYLASE (requires biotin and ATP)
• mitochondrial matrix

Question 6

Allosteric regulation of pyruvate carboxylase

Answer 6

activated by: high acetyl-CoA

Question 7

Oxaloacetate -> Phosphoenolpyruvate

Answer 7

-IRREVERSIBLE
-decarboxylation
-enzyme: PHOSPHOENOLPYRUVATE CARBOXYKINASE
(requires GTP, inducible enzyme)

Question 8

Regulation of Phosphoenolpyruvate carboxykinase

Answer 8

activated by: glucocorticoids, glucagon, retinoids

inhibited by: glucose and insulin

Question 9

Phosphoenolpyruvate -> 2-phosphoglycerate

Answer 9

• reversible

- enzyme: ENOLASE

Question 10

2-phosphoglycerate -> 3-phosphoglycerate

Answer 10

• reversible

- enzyme: PHOSPHOGLYCEROMUTASE

Question 11

3-phosphoglycerate -> 1,3-bisphosphoglycerate

Answer 11

• reversible
• dephosphorylation of ATP
• enzyme: PHOSPHOGLYCERATE KINASE

Question 12

1,3-bisphosphoglycerate -> Glyceraldehyde-3P

Answer 12

• reversible
• oxidation of NADH
• enzyme: GLYCERALDEHYDE-3P DEHYDROGENASE

Question 13

Glyceraldehyde-3P + Dihydroxuacetone phosphate -> Fructose-1,6-bisphosphate

Answer 13

• reversible

- enzyme:ALDOLASE

Question 14

Glycerol->Glycerol3P->Dihydroxyacetone phosphate

Answer 14

-enzyme: GLYCEROL KINASE

Question 15

Fructose-1,6-bisphosphate -> Fructose-6P

Answer 15

• IRREVERSIBLE
• enzyme: FRUCTOSE-1,6-BISPHOSPHATASE
• hydration

Question 16

Regulation of fructose-1,6-bisphosphatase

Answer 16

Allosteric:
inhibited by: high AMP and F-2,6-BP
activated by: high ATP

Covalent:
activated by: glucagon
inhibited by: insulin

Question 17

Fructose-6P -> Glucose 6P

Answer 17

• reversible

- enzyme: PHOSPHOGLUCOSE ISOMERASE

Question 18

Glucose-6P -> Glucose

Answer 18

• IRREVERSIBLE

- enzyme: GLUCOSE-6-PHOSPHATASE